This application claims the priority of PCT International Application No. PCT/DE99/00993, filed Apr. 1, 1999, and German patent document 198 15 436.4, filed Apr. 1, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention concerns an ion mobility spectrometer (IMS) of the type having an ionization area for ionizing a substance which is to be analyzed, forming a gaseous ion mixture, at least one ion gate neighboring the ionization area, which gate can be electrically switched between a blocked and an open state, a drift area neighboring the ion gate with an electrical drift field running along a drift path, and an ion collector that is connected to electronics to detect contacting ions.
German patent document DE 41 34 212 A1 discloses an IMS that is miniaturized by the monolithic integration of the ion source, the drift path, the collector electrodes and the required electronics, based on a semiconductor material. A concrete design of such a device that can be efficiently created, especially by means of semiconductor technology is, however, not disclosed.
In German patent document DE 196 50 612, the ion gate, the drift chamber and the ion collector of an IMS are constructed of pieces that can be cut out of conventional semiconductor materials. In particular, the ion gate is designed as a grid perpendicular to the drift direction that is comparatively involved to manufacturer using semiconductor technology. Connecting the ionization and drift chamber via the ion gate requires a substantial amount of mechanical processing.
One object of the present invention is to provide a miniaturizable IMS that is easier to design and manufacture than earlier versions.
This and other objects and advantages are achieved by the IMS according to the invention, which is based on the recognition that the previous three-dimensional gas guidance in the ionization and drift area utilized by prior art devices can be reduced to an essentially two-dimensional design. When there is a sufficiently small distance between two parallel, gas-delimiting wall surfaces, a side seal is not necessary so that one or more simple spacers are sufficient to connect the wall elements, which are pressed against the spacers via clamps, etc. With such a planar arrangement, the ion gate can be formed by planar conductor structures on the wall elements, which substantially reduces the manufacturing effort, especially since special chambers for ionization and the drift path are no longer necessary. The ion collector can also be manufactured in the same way, which represents a substantial simplification.
Given the planar design of the wall elements and conductor structures, conductive rubber contacts can be used to contact the conductive strips that are familiar from LCD technology, where they are used to contact reliably a large number of adjacent contact surfaces.